Grounded grid radio tube circuits



R. LAMBERT 2,736,777

GROUNDED GRID RADIO TUBE CIRCUITS Filed July 1, 1955 7 Feb. 28. 1956 FIG-.2

IN V EN TOR. RAYLAMBERT 4/: 47-70 Q/vEr 2,736,777 GROUNDED GRID RADIO TUBE CIRCUITS Ray Lambert, Cincinnati, Ohio Application July 1, 1953, Serial No. 365,334 5 Claims. (Cl. 179-171) My invention relates to the suppression of that portion of the signal voltage transmitted through a grounded grid thermionic tube due to the application of the signal voltage across the tube impedance between the cathode and plate and referred to here as the diode eifect.

The prblem.In a thermionic tube employing a grounded grid with cathode input load impedance a signal transfer is experienced across the tube from the cathode to the plate in the nature of a diode effect. This signal transfer occurs in addition to the action of the signal voltage applied between the cathode and grounded grid. This signal applied across the cathode-plate impedance of the tube is out or" phase with the signal component transferred due to the cathode-grid voltage and is troublesome in certain applications of the grounded grid tube, particularly in applications involving phase reversal and voltage inversion such as in radio receivers employing interference degeneration.

The s0luti0n.This undesirable diode action in the grounded grid tube may be cancelled by a degenerative circuit when using tubes provided with a grid in addition to the control grid, such as tetrodes or pentodes.

The circuit.--Fig. 1 shows a schematic wiring diagram of the circuit employed for the cancellation of the diode effect in grounded grid tubes. Fig. 2 shows a modification of this circuit.

In Fig. 1 tube 1 is shown as a pentode, with input signal voltage terminal 2 and grounded input terminal 3 and ground at 4. The signal is impressed across the signal-voltage dropping resistor 5 and the input loadimpedance resistor 6 in series, resistor 5 being shunted by condenser 7 which may be fixed or variable as desired, and resistance 6 shunted by stray capacity shown at 8. Resistor 5 may be fixed or variable as desired. Resistor 6 is the cathode input load resistor.

The portion of the input signal voltage impressed across resistor 5 and condenser 7 is applied to the screen grid of tube 1 through condenser 9. The signal voltage impressed upon the screen of tube 1 through condenser 9 is isolated from ground by resistor 10 (not bypassed by a condenser to ground) which also serves as a voltage dropping resistor from the screen voltage supply. Shown also in Fig. l is a potentiometer 11 connected between the source of high voltage supply 12 and ground which may be employed, if desired, for the purpose of controlling the voltage applied to the screen grid, the variable arm-to-ground portion of this potentiometer being shunted to ground by condenser 13. I

Instead of the method shown in Fig. 1 for applying a portion of the signal voltage to the screen through condenser 9, isolating this portion of the signal voltage from ground by resistor 10, and supplying the screen voltage of tube 1 through resistor 10, a battery may be connected in shunt with or in place of condenser 9. See Fig. 2. In Fig. 2 the identifying numbers correspond to similar numbers in Fig. 1. In Fig. 2 the .battery 22 is inserted in the lead connecting the input mesh to the screen of tube 1, the condenser 9 (Fig. 1) being eliminated. The battery 22 may, however, be shunted by a condenser.

Any of the conventional methods of securing gridcathode bias may be employed. In Fig. 1 this bias is provided by resistor 14 shunted by condenser 15 and is applied to the grid through the signal isolating resistor 16. The suppressor grid (if a pentode is employed as shown ite States Patent 9 2,736,777 Patented Feb. 28, 1956 2 in Fig. 1) may be connected to the ground directly while the grid is grounded with respect to the signal through condenser 17.

Any convenient output load arrangement may be employed. In Fig. 1 a voltage-feed load is shown at 18 (which may be reactive) and the signal output is applied across terminals 19 and 20 through the coupling condenser 21. The output load need not employ the parallel plate feed as shown and any other convenient or conventional coupling may be used as desired.

The other loading and signal voltage dropping elements in Fig. 1, shown as resistors 5, 6, 10, and 16, may be made reactive as desired.

The 0perati0n.The proper signal voltage and signal phase for the degeneration of the diode effect are secured by the selection or adjustment of resistor 5 and condenser 7 (see Fig. -1). The signal voltage across this mesh is impressed upon the screen grid so as to nullify the effect of the voltage impressed directly across the cathode-plate impedance of the tube.

In order to adjust for the cancellation of the diode effect, condenser 17, Fig. 1, is connected from grid to cathode of tube 1 instead of from grid to ground and a signal applied to the input terminals 2 and 3. The values of resistor 5 and condenser 7 are then selected for signal silence at the output terminals 19 and 20. When using an aperiodic input mesh as indicated in Fig. 1 it is possible to make this adjustment to cover a very wide band of frequencies. After making this adjustment for the cancellation of the diode eflfect, condenser 17 is reconnected between grid and ground as shown in Fig. 1.

I am aware that the device herein described is susceptible of considerable variation without departing from the spirit of my invention and, therefore, I have claimed my invention broadly as indicated by the appended claims.

I claim:

1. In a thermionic vacuum tube circuit comprising input terminals, said input terminals consisting of an input signal-voltage terminal and a grounded input terminal, a thermionic vacuum tube having a cathode, plate, control grid, a screen grid, an input load impedance connected between the cathode of said thermionic vacuum tube and ground, said thermionic vacuum tube having the signal grid connected to ground with respect to signal voltage relative to the signal voltage applied to said cathode, an output load impedance between the said plate of the said thermionic vacuum tube and ground, said plate circuit of said thermionic vacuum tube provided with output terminals whereby the signal output of said thermionic vacuum tube may be connected to utilization means, and a source of power for the cathode heater and plate and screen space currents for said thermionic vacuum tube, means are provided for applying a selected portion of the input signal voltage with controlled phase across the screen-cathode circuit of said thermionic vacuum tube, which said means comprise, in combination: an adjustable signal-voltage dropping resistor included between the above said input signal-voltage terminal and the above said input load impedance, said signal-voltage dropping resistor being in series with said input signal-voltage terminal and said input load impedance; the said signal-voltage dropping resistor shunted by an adjustable condenser; a condenser connected between the above said input signal-voltage terminal and said screen grid; a series screen current supply resistor isolating said screen from ground and connecting the above said screen grid and the above said source of power'for said screen space current; whereby the signal above said thermionic vacuum tube due to the diode effect is balanced and cancelled at the above said plate of the above said thermionic vacuum tube by the signal voltage across the screen-cathode circuit of said thermionic vacuum tube.

2. In a thermionic vacuum tube circuit comprising input terminals, said input terminals consisting of an input signal-voltage terminal and a grounded input terminal, a thermionic vacuum tube having a cathode, plate, control grid, a screen grid, an input load impedance connected between the cathode of said thermionic vacuum tube and ground, said thermionic vacuum tube having the signal grid connected to ground with respect to signal voltage relative to the signal voltage applied to said cathode, an output load impedance between the said plate of the said thermionic vacuum tube and ground, said plate circuit of said thermionic vacuum tube provided with output terminals whereby the signal output of said thermionic vacuum tube may be connected to utilization means, and a source of power for the cathode heater and plate and screen space currents for said thermionic tube, means are provided for applying a selected portion of the input signal voltage with controlled phase across the screen-cathode circuit of said thermionic vacuum tube, which said means comprise, in combination: an adjustable signal-voltage dropping resistor included between the above said input signal-voltage terminal and the above said input load impedance, said signal-voltage dropping resistor being in series with said input signal-voltage terminal and said input load impedance; a condenser connected between the above said input signal-voltage terminal and said screen grid; a series current supply resistor isolating said screen from ground and connecting the above said screen grid and the above said source of power for said screen space current; whereby the signal impressed across the cathodeplate impedance of the above said thermionic vacuum tube due to the diode effect is balanced and cancelled at the above said plate of the above said thermionic vacuum tube by the signal voltage across the screencathode circuit of said thermionic vacuum tube.

3. in a thermionic vacuum tube circuit comprising input terminals, said input terminals consisting of an input signal-voltage terminal and a grounded input terminal, a thermionic vacuum tube having a cathode, plate, control grid, a screen grid, an input load impedance connected between the cathode of said thermionic vacuum tube and ground, said thermionic vacuum tube having the signal grid connected to ground with respect to signal voltage relative to the signal voltage applied to said cathode, an output load impedance between the said plate of the said thermionic vacuum tube and ground, said plate circuit of said thermionic vacuum tube provided with output terminals whereby the signal output of said thermionic vacuum tube may be connected to utilization means, and a source of power for the cathode heater and plate and screen space currents for said thermionic vacuum tube, means are provided for applying a selected portion of the input signal voltage with controlled phase across the screen-cathode circuit of said thermionic vacuum tube, which said means comprise, in combination: a signal-voltage dropping resistor included between the above said input signal-voltage terminal and the above said input load resistor, said signal-voltage ropping resistor being in series with said input signalvoltage terminal and said input load impedance; the said signal-voltage dropping resistor shunted by a condenser; a condenser connected between the above said input signal-voltage terminal and said screen grid; a series screen current supply resistor isolating said screen from ground and connecting the above said screen grid and the above said source of power for said screen space current; whereby the signal impressed across the cathode-plate impedance of the above said thermionic vacuum tube due to the diode effect is balanced and cancelled at the above said plate of the above said thermionic vacuum tube by the signal voltage across the screen-cathode circuit of said thermionic vacuum tube.

4. In a thermionic vacuum tube circuit comprising input terminals, said input terminals consisting of an input signal voltage terminal and a grounded input terminal, a thermionic vacuum tube having a cathode, plate, control grid, a screen grid, an input load reactance connected between the cathode of said thermionic vacuum tube and ground, said thermionic vacuum tube having the signal grid connected to ground with respect to signal voltage relative to the signal voltage applied to said cathode, an output load impedance between the said plate of the said thermionic vacuum tube and ground, said plate circuit of said thermionic vacuum tube provided with output terminals whereby the signal output of said thermionic vacuum tube may be connected to utilization means, and a source of power for the cathode heater and plate and screen space currents for said thermionic vacuum tube, means are provided for applying a selected portion of the input signal voltage with controlled phase across the screen-cathode circuit of said thermionic vacuum tube, which said means comprise, in combination: an adjustable signal-voltage dropping reactance included between the above said input signal-voltage terminal and the above said input load reactance, said signal-voltage dropping reactance being in series with said input signal voltage terminal and said input load reactance; a condenser connected between the above said input signal-voltage terminal and said screen grid; a series screen current supply resistor isolating said screen from ground and connecting the above said screen grid and the above said source of power for said screen space current; whereby the signal impressed across the cathode-plate impedance of the above said thermionic vacuum tube due to the diode effect is balanced and cancelled at the above said plate of the above said thermionic vacuum tube by the signal voltage across the screen-cathode circuit of said thermionic vacuum tube.

5. In a thermionic vacuum tube circuit comprising input terminals, said input terminals consisting of an input signal-voltage terminal and a grounded input terminal, a thermionic vacuum tube having a cathode, plate, control grid, 21 screen grid, an input load impedance connected between the cathode of said thermionic vacuum tube and ground, said thermionic vacuum tube having the signal grid connected to ground with respect to signal voltage relative to the signal voltage applied to said cathode, an output load impedance between the said plate of the said thermionic vacuum tube and ground, said plate circuit of said thermionic vacuum tube provided with output terminals whereby the signal output of said thermionic vacuum tube may be connected to utilization means, and a source of power supply for cathode heater and plate currents for said thermionic vacuum tube, means are provided for applying a selected portion of the input signal voltage with controlled phase across the screen-cathode circuit of said thermionic vacuum tube, which said means comprise, in combination: an adjustable signal-voltage dropping resistor included between the above said input signal-voltage terminal and the above said input load impedance, said signal-voltage dropping resistor being in series with the said input signal-voltage terminal and said input load impedance; the said signal-voltage dropping resistor shunted by a condenser; a battery connected between the above said input signal-voltage terminal and said screen grid; whereby the signal impressed across the cathode-plate impedance of the above said thermionic vacuum tube due to the diode effect is balanced and cancelled at the above said plate of the above said thermionic vacuum tube by the signal voltage across the screen-cathode circuit of said thermionic vacuum tube.

References Cited in the file of this patent UNITED STATES PATENTS 2,553,020 Knol et a1. Dec. 5, 1950 

